Silver and the environment

Abstract

The fate of silver is traced from its solubilization during photoprocessing to its treatment in a secondary biological waste treatment plant. The potential impact of these processes on the environment is described. Silver is generally solubilized as the tightly bound thiosulfate complex during processing of photographic paper and film. Data are presented showing that this silver-thiosulfate complex is not harmful to secondary waste treatment plants and is much less toxic than free silver ion to aquatic organisms. Silver thiosulfate in secondary biological waste treatment plants is converted to insoluble silver sulfide, which is removed in the sludge. Silver sulfide does not adversely affect anaerobic digestion of the sludge. No significant amounts of free silver ion and only trace amounts of complexed and adsorbed silver are discharged to the aquatic environment. The silver incorporated into the sludge is immobile and should not restrict the use of sludge for the enrichment of soils.